A thin sheet subjected to spatially varying growth will buckle into a three-dimensional shape to lower its elastic energy.  Such processes are common in biological morphogenesis, and would provide powerful tools for the design of actuating polymer micro-devices.  While the relationship between stretching and the resulting surface curvature has been understood for almost two centuries, many questions remain regarding how a desired three-dimensional shape may be achieved by patterning the growth of a sheet with finite thickness.  To address these questions, we have developed a system of patternable, temperature responsive sheets based on photo-crosslinkable poly(N-isopropyl acrylamide) copolymers.  A simple grayscale lithographic approach provides access to sheets patterned with a small number of discrete swelling levels, yielding surprisingly rich behavior.  Further, we have developed a halftoning approach that allows printing of effectively smooth, arbitrary two-dimensional patterns with only two photo-masks.

Photo-patterned growth of stimulus-responsive gel sheets

243rd National Meeting (2012)

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